The present invention relates to an information recording and reproducing device, such as a magnetic disk drive, in which servo sectors are radially formed on a disk-shaped recording medium at regular intervals, and more particularly to a method for efficiently formatting long data sectors (hereinafter abbreviated as “long sector”).
For example, it is assumed that in a magnetic disk drive that uses a magnetic disk having a diameter of 1.0 inch (a diameter of 25.4 mm) as a recording medium (hereinafter referred to as “1.0-HDD”), a certain track has a data area, the round length of which is 80 kB (kilobyte). In this case, if the length of one data sector which is the minimum unit of read and write is as short as about 500 B (byte), the influence of a sector corresponding to the end of a round, which is exerted upon the format efficiency, is small.
It is assumed that after a round of a track, an area, the size of which is almost equivalent to one data sector, could not be formatted at a position of the end sector. In this case, if the format efficiency as a result of losses of an ECC and of a servo area is at least 80%, reduction of the format efficiency as a result of an area loss which is a little less than one data sector is as small as 0.5%=80×(1×0.5)/80.
However, a magnetic disk having a data sector whose length is as small as about 500 B has many gap areas between data sectors. Since fluctuations in revolution or the like require a long gap area, the format efficiency is decreased. Moreover, the ECC capability for each short data sector is unlikely to expect the sufficient performance enough to meet a request to reduce a bit error rate (BER) in response to future high density.
For this reason, what is considered is a long sector in which by lengthening a data sector which is the minimum unit of read and write, the number of gap areas is decreased so as to reduce a format loss factor such as fluctuations in revolution, and in which adding an ECC to a long data sector makes it possible to improve the ECC capability. The technology relating to this is detailed in patent document 1 (Japanese Patent Laid-Open No. 2002-288943).